"Do or Do not. There is no try."

It took just one year for Marco Rubio to go from Beltway darling to “bless his heart.”

Rubio, whom Florida politicos have known for years as ambition in human form, ran audaciously for the United States Senate in 2010, shoving former Republican governor Charlie Crist out of the way and out of the party in the process. He won a 49 percent plurality in a three-way race against Crist and then-Democratic Rep. Kendrick Meek to claim the office.

Even as he ran, it was clear to most Florida political watchers that Rubio viewed the Senate as a mere stepping stone to the presidency. He seized the spotlight in the crafting of an immigration reform that was his star turn. He was considered the guy who could sell the bill to the right.

But when he mounted a tour of conservative media outlets to make the pitch, he was roundly rebuffed, including by one of his constituents, Rush Limbaugh of Palm Beach. Rubio quickly abandoned his colleagues, including Arizona Senator John McCain, and disavowed the bill.

Rubio’s flight from immigration reform highlighted one of his less wonderful qualities: his willingness to morph into whatever political form suits his immediate needs. He was anointed by Jeb Bush to become speaker of the Florida House, and shoved aside his best friend at the time, speaker aspirant Gaston Cantens, to get there, figuring there was room for only one Cuban-American leader. He became a tea partier when being a tea partier was the path to Senate power; and ditched the movement soon thereafter. He’s been a neoconservative acolyte of Jeb Bush, and he’s been Bush’s tormentor, stepping in front of him in line during what friends of Jeb saw as his last chance to be president. In the process, he betrayed a man who throughout his political career had been both benefactor and de facto family.

Now, Rubio is mounting his latest reinvention; going from “never going to run for re-election” to the Senate, to maybe, to “yes.” Rubio watchers in Florida say the decision has to do with two things: the beseeching of D.C. Republicans like Mitch McConnell, who see Rubio as the party’s best chance of holding onto the seat in a tough election cycle; and Rubio’s desire to run for president again in 2020—something he believes he can best do from a Senate perch.

But getting back in involves real risks for Rubio.

The first risk: his reputation. Rubio may have cleared the field of his most prominent Republican competitors, but among those remaining is Carlos Beruff, a self-funding developer who has made it clear he is willing to put $10 to $15 million into the race on top of the $4 million he’s already spent. And Beruff is already hitting Rubio hard on the question of whether he’ll vow to serve out his full term if reelected rather than running for president and using the Senate as a stepping stone again. That’s a promise it seems unlikely Rubio can make honestly, and he has already refused to be pinned down on the matter when asked by reporters.

That future prospect is where the second risk to Rubio lies. If he gets back in and loses in a primary, particularly to a virtual unknown like Beruff, he will be humiliated. If he survives the primary but loses in November (Rep. Patrick Murphy currently leads the Democratic pack), he will be equally so. It’s one thing to cede a Senate seat willingly. Losing it would make it very difficult to run for president, given the spotlight that will be on the Florida race. Rubio seemed to seek some assurances from national conservatives this week, reportedly lobbying former rival Ted Cruz and conservative stalwart Mike Lee to essentially draft him publicly to run, to put a movement sheen on it. Both men declined.

Democrats have vowed to make life difficult for Rubio. . Murphy reacted to the announcement that Rubio was “in” with an email blast, saying the famously unhappy Senate warrior “abandoned his constituents, and now he’s treating them like a consolation prize.” Super PACS supporting Democrats have pledged to spend at least $10 million in the effort to unseat him. And Democrats could have a good shot, if Hillary Clinton beats Trump in Florida and has coattails, and if straight-laced, seemingly incorruptible Murphy is the Democratic Senate candidate.

Still, there is upside for Rubio. He is leading in the current Quinnipiac poll against either Murphy or fiery Rep. Alan Grayson. He will no doubt have flush campaign coffers, between longtime patrons like former Philadelphia Eagles owner and car magnate Norman Braman, who is said to have poured more than $10 million in the super PACs supporting Rubio’s presidential bid, and the Republican Senate Campaign Committee. But the campaign is likely to feature a rehash of his worst moments of the past few years: his immigration reversal; his disastrous “tiny bottle” moment as he delivered the State of the Union rebuttal in 2013; his failure to show up for work; his “robot Rubio” shellacking at the hands of Chris Christie during the GOP debates; his rather self-serving reaction to Orlando, which he used as the excuse for reconsidering quitting the Senate and which has drawn fire from LGBT rights groups; and his spectacular primary defeat at Trump’s hands.

There’s one more risk Rubio faces: his long-term brand.

As a Senate candidate, Rubio will be under tremendous pressure to make good on his vow to support Trump as the Republican nominee. This on top of the spectacle of someone who spent the waning days of his presidential bid playing the dozens with the man who reduced him to “Little Marco” oddly saying he would be “honored” to help Trump in any way.

As the rare nationally known Hispanic Republican, and with the presidential candidate in a desperate search for political stars to decorate his potentially B-list-laden Cleveland convention, Team Trump will surely deploy Rubio liberally, to refute the notion of Trump’s anti-Hispanic racism. But for Rubio, a primetime speaking slot in Cleveland could be more curse than blessing. He risks becoming Trump’s Hispanic human shield; a prospect other Latino politicians, like spurned New Mexico governor Susana Martinez, will be able to avoid, even if they are dragooned into attendance in Cleveland.

For so many reasons, a Rubio Senate run seems fraught with career-defining peril. But it’s peril he’s apparently prepared to face, if it means another shot at the White House.